The present invention relates to medical treatment devices. In particular, the present invention relates to measuring the distance traveled of a catheter, introducer sheath or other devices. The present invention also concerns related processes, such as measuring the energy of a treatment device, which may include a laser for vein ablation in treating varicose veins, among other things.
Varicose veins exist because valves contained in the walls of the veins fail, allowing blood to stagnate, causing noticeable purple or red traces of the vein visible from the outside of the skin. During a normal vein ablation procedure for varicose veins, a practitioner first identifies a vein or veins for the procedure. The veins are then mapped as a guide for the practitioner in order for him to perform the procedure. Once the veins are mapped, the practitioner prepares the vein for ablation by introducing a sheath into the distal end of the vein, in preparation for introduction of a treatment device, such as a laser or radio frequency device.
The treatment device is introduced into the vein at the distal end and extended in the vein to a junction with a healthy branch of a larger vein to ensure that the entire damaged vein is treated. In a laser treatment procedure, a fiber-optic member is covered by a sheath for introduction and for the treatment procedure. As fiber-optic members are usually very slender fibers of glass, it is not desirable to introduce the fiber-optic member without a covering because the fiber can break off in the patient, or can puncture the vein walls, damaging surrounding tissues.
Thus the fiber-optic member is introduced in a sheath or catheter and advanced to the beginning of the treatment area. The practitioner can determine the location of the tip of the fiber-optic member in the patient by ultrasound imaging, transillumination of the anatomy using an aiming or targeting beam, by feel, and/or by estimating the location based on a calculated position inside of the vein targeted for treatment. Once the fiber-optic member reaches the beginning of the treatment area, the practitioner exposes a portion of the fiber-optic member by extending the fiber-optic member out of the end of the sheath, exposing about 2 cm of fiber, uncovered by the sheath at the treatment end. The laser is then activated and transmits energy through the fiber, thereby heating the tissue and fluid around the end of the treatment fiber, effectively destroying the vein and preventing further filling of the vein with stagnant blood. The ablation procedure removes the appearance of the varicose vein, alleviates the pain caused by the varicose vein and prevents further complications.
In performing the ablation procedure, the practitioner must withdraw the fiber and sheath together at a rate such that neither too much nor too little energy is applied along the vein. To aid the practitioner in determining the withdrawal rate and distance the treatment sheath and fiber remain to be withdrawn, previous treatment sheaths included marks on the sheath body at periodic intervals. By counting the marks, a practitioner could determine how far the sheath had been withdrawn and by subtracting the amount withdrawn from the original inserted length of the sheath, the practitioner could then determine the length of the portion of the sheath remaining inside the patient.
Additionally, in a traditional ablation procedure, a practitioner needs to monitor the energy expended by the laser to ensure sufficient treatment of the target veins. One way to see where the end of the treatment catheter is located inside of the patient is by seeing light through the patient's skin before or during the laser treatment of the target area. Light in the visible spectrum, which may be a targeting light, may be used. Thus, practitioners often dim the lights, allowing better viewing of the monitors and of the treatment location in the patient. A practitioner may also know that an area has been over-treated by patient discomfort and pain.
Thus, in a traditional ablation procedure, a practitioner needs to identify and count markings on the catheter in very low light, simultaneously monitoring the energy output, rate of treatment, location of treatment, and patient comfort.
Some previous efforts to aid the practitioner in managing all of the requirements of the procedure include, for example, a device and method disclosed in U.S. Patent Publication No. US 2006/0217692. In the disclosed device, a system monitors the withdrawal rate and automatically adjusts the energy level of the treatment laser. However, many practitioners do not like the automatic adjustment because the practitioner is consequently limited in her ability to adjust the treatment levels for different or difficult treatment regions. This loss of control forces the practitioner to constantly monitor, second-guess, override, and adjust the machine.
Thus what is needed is a device that aids the practitioner in providing information in an easy-to read and determine format, while still allowing the practitioner control over the procedure.